Instead of wind mills, you could have gravity mills. Pump water into a higher-altitude reservoir on low-gravity days, and let it flow down – turning a turbine – on high gravity days. At least electricity would be cheap.
Or if it varies by region, pump water horizontally (or let it flow slightly downward) from a high gravity region to a low one. Then pump the water upwards there, then horizontally again to the high gravity region. Then let it fall down to turn a turbine that runs all the pumps – perpetual motion (ish)!
Predicting tides becomes hard. Everything is going to be really windy all the time, as the atmosphere expands in low-gravity regions and contracts in high gravity ones. This makes tall buildings impractical, as they would also have to be built for some maximum gravity rating on top of the constant gravity storms.
The oceans would be weird, and violent. Hurricanes might get far more powerful than what we deal with, if the right gravity conditions occur.
For any sort of civilization to emerge, gravity would have to change/vary really slowly. I don’t even want to think of orbits. Kerbal Space Program would be like, really hard in that universe.